It was just the news Brendon McCullum didn't want to hear on the eve of the Twenty20 series against South Africa - the New Zealand cricket captain has lost the spearhead of his pace attack for the entire tour.

McCullum was already without in-form Tim Southee for the Twenty20 series - he stayed home to be with his partner for the birth of their child, expected today or tomorrow - but a thumb ligament injury sustained while fielding for Northern Districts against Wellington in a Plunket Shield match this week has put a line through any involvement in the tests and one-dayers.

Southee will be out for six to eight weeks, putting him in doubt for the start of the England tour and propelling South African-born Neil Wagner and veteran Chris Martin into contention for the two tests in South Africa.

McCullum described Southee's absence as "a huge loss" when he fronted the press in Durban overnight (NZT) ahead of tomorrow's first T20 at Kingsmead.

"Tim's been our No 1 bowler in test cricket for the last wee while, and also the one-dayers as well, he's a real leader of the attack even at such a young age, so he's going to be a huge loss," the new skipper said of the 24-year-old who took 20 wickets at 14.90, including 8-120 in New Zealand's 167-run win over Sri Lanka in Colombo last month, in his last three tests.

"Our thoughts are with him because I know he had a keen eye on this series, to test himself out against some of the world's best bowlers in (Morne) Morkel, (Dale) Steyn and the like. I guess what it does do is give somebody else an opportunity, so we'll welcome whoever that is."

On a brighter note, McCullum said there was a "high level of excitement" among the new-look New Zealand squad ahead of the three-match T20 series, particularly after Wednesday's 24-run warmup victory over South Africa A, which he described as a confidence-booster.

All five newbies played in that match, though McCullum suggested there would be "a couple" of changes for the first international.

The players coming in are most likely to be opening batsman Martin Guptill and allrounder Doug Bracewell, who both sat out the warmup.

"I think the guys have prepared pretty well. Obviously tomorrow is a huge step up but we see it as an opportunity for this team," he said.

McCullum felt the Kingsmead pitch was on the dry side, compared to what they had expected, and that would be reflected in the playing 11. New Zealand have three useful T20 spinners in the squad, Nathan McCullum, Ronnie Hira and Rob Nicol.

"If it is slow hopefully we'll be able to utilise the players we have in the team, take some pace off the ball and put pressure on South Africa through that," he said, saying Wednesday's win provided them with a blueprint for a slow pitch.

"The key there was the early wickets, we took some early wickets and allowed our spinners to get into the game early against a middle order trying to settle. That's a pretty good blueprint in any Twenty20 game, early wickets, bring the spinners in and try and dry up the run-rate through pressure in the field."